The exterior parts of watches and similar devices observe numerous constraints, in particular as regards sealing, robustness and appearance, and must be designed to prevent any inadvertent disassembly, inevitably requiring after sales work to change gaskets, perform cleaning, lubrication, or even repair.
Some exterior or control components must also be angularly indexed with respect to each other, to locate original reference, rest or actuation positions, or to facilitate the reading of indications or graduations, or to ensure the continuity of warped surfaces and/or of decorations. This angular indexing is often difficult to achieve successfully in conjunction with properly clamped components and perfectly sealed gaskets.